In the chemotherapy of bacterial infections, particularly the chemotherapy of infections by acid-fast bacteria, there have already been used, as antibacterial agent, antibiotics such as rifampicin, kanamycin, streptomycin, viomycin, capreomycin, cycloserine, and the like.
A serious problem for the chemotherapy of the bacterial infections is in that bacteria causative of the bacterial infections become drug-resistant. In particular, the appearance of acid-fast bacteria which are resistant to rifampicin, kanamycin, streptomycin, viomycin, capreomycin, cycloserine and the like has brought about a social problem in respect of the chemotherapy of the acid-fast bacterial infections. Thus, there is now a keen request for providing a novel chemotherapeutic agent which is effective against bacterial infections as induced by the acid-fast bacteria resistant to the antibacterial drugs. Strongly requested also is a novel chemotherapeutic drug that is effective against the bacterial infections which are induced by atypical acid-fast bacteria and for which no chemotherapeutic treatment has been established yet.
In order to meet these requisites, therefore, there exists a strong demand to find out or to create novel compounds which have novel chemical structures and can exhibit excellent properties such as high antibacterial activities in a different way from those of the known antibiotics as hitherto utilized. We, the inventors of this invention, have carried out various investigations with the intention of providing novel antibiotics having excellent antibacterial activities which can meet the above-mentioned requisites.
Thus, there have already been proposed antibiotics, caprazamycins A, B, C, E and F which have been produced from Streptomyces sp. MK730-62F2 strain (deposited under the depository number of FERM BP-7218 under the Budapest Treaty) and which exhibit high antibacterial activities against acid-fast bacteria [see Pamphlet of PCT International Publication Number WO 01/12643A1 and European patent application first publn. EP 1211259A1].
Caprazamycins A, B, C, E and F are compounds represented by the following general formula (A)
wherein R is tridecyl group for caprazamycin A, 11-methyl-dodecyl group for caprazamycin B, dodecyl group for caprazamycin C, undecyl group for caprazamycin E, and 9-methyl-decyl group for caprazamycin F.
Further, there have also been provided caprazamycins D, G, D1 and G1 which are produced from Streptomyces sp. MK730-62F2 strain (FERN BP-7218) (refer to the specification of PCT application No. PCT/JP02/13386 filed on Dec. 20, 2002).
Caprazamycin D and caprazamycin G are the compounds represented by the following general formula (B)
wherein R is 10-methyl-undecyl group —(CH2)9CH(CH3)2 for caprazamycin D and is 9-methyl-undecyl group —(CH2)9CH(CH3)CH2CH3 for caprazamycin G.
Caprazamycin D1 and caprazamycin G1 are the compounds represented by the following general formula (C)
wherein R is 10-methyl-undecyl group —(CH2)9CH(CH3)2 for caprazamycin D1 and is 9-methyl-undecyl group —(CH2)8CH(CH3)CH2CH3 for caprazamycin G1.
There have also been known liposidomycins A, B and C which are produced from Streptomyces glyceosporeus SN-1051M (FERM BP-5800) (refer to Japanese Patent Application First Publication KOKAI Sho-61-282088).
Liposidomycins A, B and C are compounds represented by the following general formula (D)
wherein R is 4,7-tridecadienyl group —(CH2)3—CH═CH—CH2—CH═CH—(CH2)4—CH3 for liposidomycin A, 9-methyl-decyl group —(CH2)8—CH(CH3)2 for liposidomycin B and undecyl group —(CH2)10—CH3 for liposidomycin C.
Further, there have been known liposidomycins G, H, K, L, M, N and Z and other liposidomycins' homologues (refer to Pamphlet of PCT International Publication Number WO97/41248 and European Patent Application First Publication, EP 1001035A1).
Also known already are liposidomycins X-(III), Y-(III), Z-(III), C-(III), V-(III), A-(III), G-(III), M-(III), K-(III), and N-(III) (see European Patent Application First Publication EP 1001035A1) and they are compounds represented by the following general formula (E)
wherein R is a long chain alkyl group shown in the Pamphlet of WO97/41248 or in Table 1 of the European Patent Application Publication EP1001035A1.
A report has been issued that relates to investigation on elucidation of chemical structures of liposidomycins A, B and C [refer to The Journal of Organic Chemistry, Vol. 57, No. 24, pages 6392-6403 (1992)]. This report describes (see the J.O.C., pages 6397-6399) three compounds, namely, compound 10 (given as anhydrodeacyl-liposidomycin having molecular weight of 557) of the following planar structural formula (F)
and Compound II (given as anhydrodeacyl-liposidomycin having molecular weight of 637) of the following planar structural formula (G)
and Compound 12 of the following planar structural formula (H)
each of the three compounds having been prepared by an alkaline hydrolysis of a mixture of liposidomycins B and C in a dilute aqueous NaOH solution at 37° C. to produce Compound 10 and Compound II and by a reductive deacylation of a mixture of liposidomycins B and C with LiBH4 to produce Compound 12. The report also shows 13C-NMR data (Table III) and 1H-NMR data (Table IV) of these three compounds, but the stereo-structures of these three compounds are unknown yet until now.
Caprazamycins A to G referred to in the above have one common skeletal structure with each another and have excellent antibacterial activities. However, the antibacterial activities of caprazamycins A, B, C, D, E, F and G are different, among them, depending upon the nature of bacteria. Further, upon the preparation of these caprazamycins by the cultivation of Streptomyces sp. MK730-62F2 strain referred to above as a caprazamycin-producing bacterial strain, followed by the recovery of the caprazamycins from the resulting culture broth, it is usual that a mixture of caprazamycins A to G is first obtained. Thus, it is necessary, in order to separate the caprazamycins A to G from each other, to carry out time-consuming and troublesome operations necessarily comprising the high performance liquid chromatography (HPLC).
Therefore, it has been requested to synthesize certain novel semi-synthesized antibiotics which can have antibacterial activities equivalent or superior to those of caprazamycins A, B and C-G, and which can be prepared in an efficient way by utilizing a mixture comprising two or more of caprazamycins A to G or by utilizing any one of caprazamycins A, B or C, alone. It has also been requested to provide certain novel semi-synthesized antibiotics which comprise the skeletal structure common to caprazamycins A to G.